There's a reason the San Joaquin River has been labeled one of the hardest-working streams in the country.

Most of its flow is diverted to cities and farms before it ever reaches Stockton.

State officials are poised to address that for the first time in almost two decades, but their proposal to increase flows from less than 30 percent to 35 percent is under attack from two fronts - from water users who warn that farmland will be fallowed and jobs lost, and from environmentalists who say the increase doesn't go nearly far enough.

The State Water Resources Control Board will hear their concerns at a meeting Wednesday. The board says 35 percent strikes a balance between the needs of fish and water users.

The amount of flow is not the only issue up for discussion, though. The board also has proposed relaxing rules determining how much salt can accumulate in south Delta waterways, to the concern of farmers there.

"They're giving up on the Delta," said John Herrick, a Stockton-based attorney for the South Delta Water Agency.

These proceedings are just a first step. The water board also plans to examine flows on the Sacramento River and to determine how much water should ultimately be allowed to flow through the Delta - key determinations as Gov. Jerry Brown pursues construction of twin tunnels to divert freshwater away from the estuary.

For now, the plan is to send more water down three tributaries of the San Joaquin: the Stanislaus, the Tuolumne and the Merced rivers. Those streams were historically flush with Sierra snowmelt in the spring and early summer, and were significant breeding grounds for salmon.

Now most of the water is held back in reservoirs or diverted to cities like Stockton. The Stanislaus River alone is blocked by 28 dams.

The new proposal would allow 35 percent of the flow to pass through from February through June, when fish need help getting downstream.

But that's not enough, environmentalists say. A previous report found that if economic factors were not considered, 60 percent of the natural flow would be needed to truly sustain the ecosystem.

"The San Joaquin is the poster child for how not to manage a river," said Gary Bobker, program director for The Bay Institute in San Francisco.

A modest increase to barely more than one-third of its natural flow will not save the stream, he said. He called the proposal a "marked failure" in the first test of the board's commitment to protect the environment.

Stockton environmentalist Bill Jennings blamed the board for limiting the increased flows to the lower San Joaquin, below the Merced.

"Basically they're insisting the three tributaries of senior water rights holders have to bear the burden, and it's absurd," he said.

The water board says it didn't include the upper San Joaquin because there aren't fish there now. It might consider mandating flows on that part of the river in the future if an ambitious restoration effort currently underway proves successful.

For the lower streams, the 35 percent figure is bigger than it sounds, the board argues, and it's a flexible target that could go up or down based on how fish respond.

"Thirty-five percent really is a significant increase in flows," said Diane Riddle, an environmental program manager for the state board. She noted that the Tuolumne is as low as 19 percent of its natural flow.

"Considering other agricultural uses and groundwater impacts, we thought 35 percent is an appropriate place to start, and work from there," Riddle said.

Just as angry as the environmentalists are the water districts tapping the three rivers. A group of them called the San Joaquin Tributaries Authority has mobilized to fight the plan, warning it would have a "devastating" impact on the economy by fallowing 128,000 acres of farmland and eliminating 460 jobs. It also could force remaining growers to draw more upon precious groundwater, they say.

For perspective, the board's report says that releasing more water would reduce the region's agricultural output by about 1 percent.

Nevertheless, the water districts argue that it's unclear whether more water will equal more fish. Flows aren't the only problem for salmon; invasive fish species like striped bass are known to gobble them up.

"The 35 percent number seems, at least to us, to have no rationale and no scientific basis behind it," said Allen Short, formerly the general manager at Modesto Irrigation District, and now the director of the tributaries group. "We've made investments in water releases down tributaries over the years and we have not seen a significant improvement in salmon."

Jeff Shields, manager of Manteca-based South San Joaquin Irrigation District, warned that shooting more water down the Stanislaus would drain New Melones Lake roughly once every five years.

"Empty," he said.

Stockton could be harmed because it now receives a portion of its water supply from that reservoir. So do farmers on the east and south sides of the county.

According to state board documents, however, the impact will be far greater on the Tuolumne and Merced streams whose flows today are typically lower than the Stanislaus.

In the big picture, like other observers, Shields fears releasing extra San Joaquin water is an attempt to make up for sending more Delta water south through the proposed twin tunnels.

If the Delta's Sacramento River water is siphoned away, some other stream will have to make up for it.

"That's exactly the intention here: To be able to flush the toilet and use our water to do it," Shields said.

Riddle, with the water board, said that's not the case.

"We do intend to look at (state and federal) project impacts," she said.

And she acknowledged that simply sending more water downstream won't solve all the Delta's problems.

"There are a lot of pieces to the puzzle that need to be brought together," Riddle said.

Lumped in with the debate over river flows is a plan to ease up on salt restrictions in the channels of the south Delta.

Salt is a plague for farmers, since it can stunt the growth of their crops. Salt comes from many sources - drainage from farms, discharge from city wastewater treatment plants, and the sheer lack of water in the San Joaquin, for starters.

A standard for salt in the south Delta was set in 1978, but enforcement was delayed for many years and today the standard is routinely violated.

Critics blame the mass export of water from the Delta into the state and federal aqueducts, and say the move to weaken the standards is an attempt to make those violations less prevalent on paper while maintaining the status quo on water quality.

"Since they're not going to enforce the rules, they thought they'd change them," said Herrick, the south Delta attorney. "But this must be the only instance in the United States of America where a regulatory body is trying to relax water quality standards. That's just insane to me."

The water board argues that the amount of salt in the Delta right now is "suitable for all crops," based on a study which Herrick says does not reflect real conditions on the ground.

"A couple of years ago one guy had to replant tomatoes because the salt ruined him," Herrick said. "We have continuing salt impacts and the notion that we can deal with this quality of water, or worse, is simply false."

Salt in the south Delta is not just the farmers' concern. Everyone in Stockton would have to pay if the city is someday ordered to improve its treatment plant to reduce the amount of salt in the treated wastewater it releases into the estuary.

The state board's plan says that even with the weaker proposed standard, Stockton and its ratepayers could still be on the hook.

Nothing is certain, said Jeff Willett, assistant director for Stockton's Municipal Utilities Department. The city is due for a new discharge permit next fall, but the amount of salt it releases has been declining because the city is relying less on saltier groundwater.

Stockton may, in fact, be close to meeting the board's proposed new limit, except for the fact that the new standard is based on 30-day rolling averages as opposed to an annual average, he said.